Scientific Forecaster Discussion
fxus66 klox 221131
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
431 am PDT Mon Oct 22 2018
Temperatures will continue to trend cooler to near normal for this
time of year through mid week. High pressure will cause
temperatures to turn significantly warmer again late this week
with offshore winds expected. Areas of night through morning low
clouds will return through at least mid week.
Short term (tdy-wed)...22/304 am.
Latest fog product imagery indicated widespread low clouds across
the central coast and the Santa Ynez Valley as well as much of the
l.A. County coast and coastal valleys early this morning. Latest
amdar sounding around lax showed the marine layer around 2,000 ft
deep which makes sense with the intrusion of stratus into the
Synoptically, the upper level trough axis will linger across
Southern California through Tuesday night before exiting east
while a west to east elongated upper level ridge develops across
the eastern pac west of southern and central cal. This ridge will
begin to nudge eastward into the area by Wednesday. The upper
ridge will then expand and strengthen further inland allowing
more significant warming late this week with increasing offshore
flow late this week.
As for today, high temps will trend slightly cooler as onshore
flow increases, but will not be strong by any means. However,
boundary layer temps and 500 mb heights will continue to trend
slightly lower allowing for the modest cooling from yesterday.
Tuesday should be slightly warmer as the upper low begins to shift
to the east. High temps for today and Tuesday will be around
normal for this time of year for much of the forecast area. Some
northerly winds will affect the sba South Coast this evening, but
will remain well below advisory levels. There will continue to be
night through morning low clouds affecting most coast and coastal
valleys tonight into Tue morning and once again Tue night into Wed
morning. Not as confident that low clouds will reach the sba
South Coast due to the northerly winds this evening. However,
there could be a southerly surge from Oxnard moving up the coast
by sunrise or a few hours before. Some additional warming is
expected on Wednesday as onshore flow weakens while the upper
ridge starts to strengthen as it nudges in over the region. High
temps should increase 2 to 5 degrees for the most part. Best
warming across the valleys and inland areas.
Long term (thu-sun)...22/326 am.
Both the ec and GFS remain in good agreement with large scale
features through the weekend. An upper level ridge will build in
from the eastern pac. At the lower levels, northerly winds will
develop Thursday and then shift to the northeast by Friday
bringing more Santa Ana winds to the wind prone areas of Los
Angeles and Ventura counties. At this time, winds are not looking
to strong, but the high temps will rise significantly Thursday and
Friday. Highs are expected to reach the mid to upper 80s for
coast and coastal valleys with the offshore flow. There will be a
chance that by Friday highs in some inland coast or coastal
valleys locations will reach the lower 90s. Not much change on
Saturday. Grads will be a little less offshore so there will be
weaker morning canyon winds. Max temps will likely be unaffected
and will be very close to friday's warm values.
The ridge should begin to weaken on Sunday and there will be good
onshore trends (much like yesterday this will lead to 3 to 6
degrees of cooling across the coasts and vlys.
At 11z at klax, the marine layer depth was around 2000 feet. The
top of the inversion was at 3200 feet with a temp of 19c.
Areas of low clouds in most coastal areas (except in coastal
sections of vtu county), in the San Gabriel, San Fernando, the
Salinas and Santa Ynez valleys. Conditions were mostly IFR to
LIFR, except low MVFR across coastal sections of l.A. County.
Expect skies to clear by mid morning in the valleys, and by late
morning or early afternoon across the coastal plain. Expect
widespread low clouds in coastal and most valley areas tonight,
with generally IFR conds, except LIFR conds on the central coast
and low MVFR across the l.A. County coast.
Klax...moderate confidence in the 12z taf. Cigs are expected to
clear by late morning or around noon. There is a 20% chance that
cigs could drop into the IFR category for a few hours between 12z
and 16z. There is a 20% chance that cigs could linger until 21z.
There is a 20-30% chance that cigs will arrive as early as 04z
Kbur...moderate confidence in the 12z taf. Cigs are expected to
clear by mid morning. There is a 20-30% chance that cigs
linger through 18z. There is a 20-30% chance that cigs will
arrive as early as 07z this evening.
For the outer waters, moderate to high confidence in the forecast.
Small Craft Advisory (sca) conds are expected thru at least late
tonight. Conditions should drop below Small Craft Advisory levels very late tonight
thru Tue morning, the Small Craft Advisory conds are likely Tue afternoon thru Thu.
For the inner waters north of pt Conception, moderate to high confidence
in Small Craft Advisory conds this afternoon/evening. There is a 40%-50% chance of
Small Craft Advisory level conds during the afternoon/evening hours Tue thru Thu.
For the inner waters S of Point Conception, Small Craft Advisory conds are not
expected through Fri, except there is a 20-30% chance of Small Craft Advisory
level gusts across western portions of the sba channel during the
late afternoon and evening hours Tue thru Thu.
Pz...Small Craft Advisory in effect from 3 PM this afternoon to 9
PM PDT this evening for zone 645. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Tuesday for
zones 670-673-676. (See laxmwwlox).
Hazard potential outlook (wed-sun).
A significant warming trend is possible late next week.